Evidence of NK cell activation by IPH2101. (A) Left panel: Increased expression of CD69 24 hours after first administration of IPH2101 compared with baseline (P = .016) for all patients. Center and right panels: Increased expression of CD69 (P = .0009) and CD25 (P = .026) in patients (n = 11) receiving IPH2101 doses > 0.075 mg/kg, suggesting a dose-response effect regarding NK-cell activation (as this was not observed in patients who received < 0.075 mg/kg). (B) IPH2101 binding appears to correlate with NK-cell activation. Data shown are from n = 8 evaluable subjects on the 3 mg/kg extension cohort where the percentage of IPH2101(+) NK cells appears to correlate with NK cell expression of CD107a (P = .000000093), CD25 (P = .00000000012), and CD69 (P = .01).